I had the same issue when updated to 1.5.7
Usually, you have the very first companion you hired as "bodyguard" with you and your other companions are spread out over the whole town. After my update i couldn´t find anyone of them when pressing ALT and even my bodyguard wasn´t with me.
Then I found them : They were all hanging around in the tavern. Thats not a joke, they were actually all there. When i first tried to gather them via the dialogue option (inside the tavern) the game crashed.
Then I tested via trial and error a bit... I disbanded the army I led at that time and put all my companions into the town, left the town with my party, reentered town and took back my companions into the party.... Same issue, I found them AGAIN in the tavern. But THIS time, when i used the "gather all my companions-dialogue" inside the tavern, the game didn´t crash and when entering the town through the taverns door, they all "followed" me out and spawned right beside me and followed me afterwards (like it allways happenes when you gathered your companions once before and reenter the same town or settlement again.) So this time it worked somehow ok, however it´s not very practicable if this should be a new feature (having to collect your folks in the tavern every time). And I´m quite concerned that this might be a new source of recurrent crashes.
ADDENDUM : When i searched for my companions in the town by pressing ALT, i witnessed another issue : The house of one of the gangleaders was shown (like when you have this "Prodigal son-quest" active, which I hadn´t at that time). And it was shown at three different locations.
Edit : I momentarily try to upload my savegame via upload.taleworlds.com but I get the message "upload aborted" and the site is stuck.
OK, upload worked after some time... but this stupid "upload aborted" message HAS TO BE designed to confuse confused people even more, am I right?